Starch is a natural polymer composed mainly of two major polysaccharides, namely the linearly linked amylose and the branched amylopectin. Starch possesses thermoplastic behavior though it exits in granular form in its natural state. Starch can be transformed into at molten plastic state, known as thermoplastic starch (TPS), when subjected to shearing force at a temperature of 90 to 180° C. in the presence of suitable plasticizer. In the thermoplastic starch, the weaker hydrogen bond between the polysaccharides and the plasticizer replaces the original inter-polysaccharides hydrogen bond rendering the thermoplastic starch soft and ductile. Specifically, the new bonding between the plasticizer and the polysaccharides greatly reduces the secondary bonds holding the long chain polysaccharides. In view of that starch is a renewable resource, thermoplastic starch is a sustainable product. Yet, it suffers from two major shortcomings, high water solubility and poor mechanical strength, compared to conventional synthetic plastic. In order to improve TPS mechanical property and reduce its water absorbing properties, modification have been made to the TPS. For example, European patent application no. 0327505 describes a polymeric blend of TPS and water insoluble synthetic thermoplastic polymer claiming a derived polymeric composition with better mechanical property and reduced water solubility. Guy et. al. claims another TPS derived thermoforming compound containing at least one hydroxycarboxylic acid salt that the compound acquired is claimed to have maximum loss tangent in wide range of temperature in Canadian patent application no. 2060409. Further TPS modification can be found in International patent publication no. 03074604 which provides TPS-grafted polymers formed using compatibilizer instead of plasticizer to reduce water absorption into the formed polymer. Co-continuous TPS substantially free of water is described in U.S. Pat. No. 6,605,657 and TPS reinforced by particulate filler is disclosed in another U.S. Pat. No. 6,231,970.
In recent years, a lot of effort has been put into utilizing agro-industrial wastes for the manufacturing of value-added products such as biofuels, biomaterials and the like. Recycling these agro-industrial waste can alleviate environmental problems associated with the waste disposal and reduce dependence on petroleum resources. Considering that TPS is a product necessary using starch as the major forming constituent, it is practical to employ such waste of agro-industrial in its production as long as some technical problems inherited from such use are solved. For instance, agro-industrial waste contains much lower starch content compared to normal starch granule that TPS derived thereof may fail to attain the desired plasticity and degradability. Yet, the present invention provides an agricultural waste-derived TPS composition possessing physiochemical properties which meets the industrial acceptable standard in terms of mechanical properties as well International definition for a bio-based material.